The invention herein described was made in the course of or under a contract or subcontract thereunder with the Department of the Army.
1. Field of the Invention
The present invention relates to fine leveling of a support mounted at least on one leg.
2. Description of the Prior Art
There are many mechanisms or applications which require leveling, such as transits, levels, telescopes, cameras, theodolites, and any pointing and tracking system requiring elevation and angulation operations.
One conventional system utilizes thumb screws opposed to each other to drive a two-axis gimbal or to rock a platform. Alternatively, one screw may be opposed by a spring to take up back-lash. Several problems are associated with such leveling arrangements.
Any off-center load weight over the screw increases the effort needed to turn the screw to effect the adjustment except, with respect to a turnable load, the load may be rotated so that its weight may be used to advantage. Also, the screw adjusting mechanism is located adjacent to the equipment to be levelled, in a crowded area where space limitations prevent the diameter of the screw to be enlarged; therefore, it becomes difficult for the operator to turn the screw. Additionally, such screw adjustments provide for a small mechanical advantage which, even for fine adjustments, require the exertion of large forces. Such exertion may be fatiguing to the operator and his thumb; furthermore, a large force over a small adjustment frequently results in an over-adjustment as the screw is suddently moved past the point needed to effect the proper level. A further disadvantage is that a large number of intricate parts are used and these parts exist at critical points of the tripod, specifically, at the center of the tripod load attachment point. As a consequence, the platform is made less stiff and rigid and, therefore, less stable. The complexity of the leveling mechanisms not only increases the cost of manufacture but also increases the need to maintain or repair the equipment which, especially in the field, may not be possible. A further disadvantage is that the tripod, through use of a large number of intricate parts, becomes quite heavy and not easily transportable.